Chromosomal analysis of centromochlus heckelii (Siluriformes: Auchenipteridae), with a contribution to centromochlus definition

Abstract

Historically, there are divergences in the species allocation between Centromochlus and Tatia. This study aimed to generate the first cytogenetic data about Centromochlus and, by analyzing a population of Centromochlus heckelii from the Amazon River basin, to contribute as evidence to a historical taxonomic dilemma. Diploid number of 46 chromosomes and a heteromorphic pair was found in the female karyotypes, thus characterizing a ZZ/ZW sex chromosome system. Pale blocks of heterochromatin were located in centromeric regions of some chromosomes; however, the exclusive female chromosome (W) is almost entirely heterochromatic. AgNORs were detected in terminal position on the short arms of one acrocentric pair in males and two chromosome pairs in females, the acrocentric plus the sex chromosome pair. Notable differences between Centromochlus heckelii and previous data about species of Tatia are: lower diploid number, presence of a sex chromosome system and multiple AgNORs in Centromochlus, while species of Tatia have simple AgNORs and the absence of acrocentric chromosomes. Results in this study show that chromosomal markers could contribute as evidence to taxonomic delimitation studies.